The present invention is directed to joints connecting cable repeaters to lengths of fiber optic cable, and, more particularly, to a connecting joint for a cable repeater having improved bending capability.
Fiber optic cable laid undersea is typically required to traverse great distances. Cable repeaters are well known to be placed in-line at desired intervals along the cable to receive, amplify, and retransmit the signal being carried by the cable. A bend limiting device, having a rubber boot, is typically secured to the end of the cable. The repeater is connected to the bend limiting device, with connecting optical fibers extending through the bend limiting device. To deploy the fiber optic cable, it is coiled onto large drums on a ship. Consequently, the repeaters become wrapped about the drums along with the cable. Due to the nature of the signals, and the ever increasing amount of information being transmitted in the optical fibers, repeaters are getting larger, and their increased length creates problems as they are coiled around a drum. Although the drums may be up to 9-12 feet in diameter, current repeaters may approach 5xc2xd feet in length, and, therefore, are not able to lie flat, or even substantially flat, along a drum. Tremendous stresses due to forces on the order of up to 100,000 pounds are encountered at the connection point between the repeater and the fiber optic cable to which it is attached, especially during paying out and reeling in of the cable.
Consequently, a gimbal may be provided at each longitudinal end of the repeater, to which the bend limiting devices are attached. A gimbal, as used herein, refers to a device having two mutually perpendicular and intersecting axes of rotation. A gimbal provides free angular movement in two directions. The bend angle allowed by the gimbal between the repeater and bend limiting device is limited to approximately 50xc2x0 or less as exceeding this angle at a pivot point can damage the optical fibers.
A repeater for attachment to a fiber optic cable and its end connecting structure as known in the prior art are shown in FIG. 1. Repeater 2 has a cone 5 enclosing each end thereof (only one end is shown for simplicity), and a gimbal 4 contained within cone 5. Gimbal 4 is formed of a first ring 6 secured to the cone 5 of the repeater 2. A second ring 8 sits within and is pivotally connected to first ring 6 by a pair of coaxial pins 10, only one of which is visible in the drawing. The axes of pins 10 are perpendicular to a longitudinal axis L of repeater 2. A connecting link 12 is pivotally connected at a first end thereof to the second ring 8 by a pair of coaxial pins 14, only one of which is visible. The common axis of pins 14 extend perpendicular to the common axis of pins 10, and pins 14 move in a plane which is perpendicular to the common axis of pins 10 as ring 8 pivots about pins 10. Connecting link 12 is connected at its second end to a bend limiting device 16. A bend limiting device 16 is located at the end of a boot 19 proximate the repeater 2. The end of a segment of a fiber optic cable 17, excluding the optical fibers thereof, is attached to and housed within the boot 19, as seen in FIG. 3. Optical fibers (not shown) extend through the connecting link 12 to carry signals to the repeater 2. The bend limiting device 16 prevents the relative rotation between the repeater 2 and the boot 19 from exceeding a predetermined maximum bend angle a by abutting with the first ring 6 or another part of the gimbal 4 when the predetermined maximum bend angle xcex1 is reached. This in turn prevents the fibers from becoming damaged. A commonly used maximum bend angle xcex1 between the longitudinal axis L of repeater 2 and the longitudinal axis B of bend limiting device 16 allowed by gimbal 4 is approximately 50xc2x0, thereby limiting the ability to wrap repeater 2, and fiber optic cable 17 to which it is attached, around a drum for effective deployment.
It is an object of the present invention to provide a cable repeater connecting joint which reduces or wholly overcomes some or all of the aforesaid difficulties inherent in prior known devices. Particular objects and advantages of the invention will be apparent to those skilled in the art, that is, those who are knowledgeable or experienced in this field of technology, in view of the following disclosure of the invention and detailed description of preferred embodiments.
The principles of the invention may be used to provide a cable repeater connecting joint having improved bending capability for fiber optic cable systems. A repeater is connected by a pair of joints and a coupling to a bend limiting boot assembly. In a preferred arrangement, each of the joints have two mutually perpendicular and intersecting axes of rotation. The bend limiting boot assembly encloses an end of a length of cable. Such a connecting system increases the ability to wrap the cable with its attached in-line repeater and associated structure around a drum by reducing the critical bend angle without sacrificing strength or exceeding any predetermined optical fiber bend limits.
In accordance with a first aspect, a connector for connecting a cable repeater to a length of cable includes a cable repeater having a joint. The cable repeater joint has two mutually perpendicular and intersecting axes of rotation. A coupling has a joint having two mutually perpendicular and intersecting axes of rotation. A first connecting link is pivotally connected at a first end thereof to the cable repeater joint and secured at a second end thereof to the coupling. A second connecting link is pivotally connected at a first end thereof to the coupling joint and secured at a second end thereof to a length of cable.
In accordance with another aspect, a connector for connecting a cable repeater to a length of cable includes a cable repeater having a first gimbal. A coupling has a second gimbal. A first connecting link is pivotally connected at a first end thereof to the first gimbal and secured at a second end thereof to the coupling. A second connecting link is pivotally connected at a first end thereof to the second gimbal and secured at a second end thereof to a length of cable.
In accordance with yet another aspect, a cable system includes a plurality of repeaters. Each repeater has a repeater gimbal at each end thereof. Each of a plurality of couplings has a coupling gimbal therein. The cable system also includes a plurality of first connecting links. Each first connecting link is pivotally connected at a first end thereof to a repeater gimbal and secured at a second end thereof to a coupling. A plurality of bend limiting devices is also provided. Each bend limiting device encloses an end of a length of cable. Each of a plurality of second connecting links is pivotally connected at a first end thereof to a coupling gimbal and secured at a second end thereof to a bend limiting device.
From the foregoing disclosure, it will be readily apparent to those skilled in the art, that is, those who are knowledgeable or experienced in this area of technology, that the present invention provides a significant advance. Preferred embodiments of the cable repeater connecting joint of the present invention can provide improved bending capability and, consequently, reduce the stress encountered as a repeater and cable to which it is attached are wrapped around a drum. These and additional features and advantages of the invention disclosed here will be further understood from the following detailed disclosure of preferred embodiments.